Most current valves of the in-line shut off type having a threaded plug (operator) which when fully back seated to allow flow, are secured in place by only the last two threads adjacent to the male seat and are reliant only on a retaining (snap ring) to maintain this bullet like plug in place, thus allowing the potential ejection of the deadly missile under normal operating pressures. When improper torque is applied to the backseating operator and it is turned only one or two turns too many, thus causing the snap ring to pop out allowing the plug to eject and become a bullet like missile while at the same time causing a loss of the entire charge of refrigerant, discharging into the atmosphere, which may contribute to serious environmental hazards as well as personal injury and/or death to servicing technicians and any bystander.
Additionally, valves of this type design with the threads missing from the middle of the plug and thus leaving only two or three threads to secure it in place when fully backseated also present and allow for extra wear on the remaining threads and "O" ring when using a long hexagonal wrench (tool), thus allowing sway back and forth particularly in a tight spot for working the operator or on a slight angle resulting in a leaky operator and/or "O" ring exacerbating the high risk/missile ejection possibility.
The prior art contains valves disclosed in U.S. Pat. No. 3,916,947 issued to Paul M. Holmes et al (1975), U.S. Pat. No. 686,854 issued to Charles E. Huxley (1901), U.S. Pat. No. 1,743,413 issued to Albert J. Weatherhead Jr. (1930).
The Holmes patent discloses a manifold internally threaded and a cylindrical wall is formed within the stem. The stem is also provided with an annular groove for receiving a snap ring designed to prevent the plug (operator) from being removed while operated by a hexagonal wrench (tool). The wrench which is an external tool and not an integral part of the valve is used to axially rotate the plug in and out closing or opening the valve repeatedly. It is this type of valve which the Retaining Snap Ring Adapter is specifically designed to overcome its dangerous and unsafe properties.
The Huxley patent discloses a valve comprising a hollow casing, a valve seat, a valve closure, a stem for actuating said closure, and a cylinder bushing which fits within a cylindric recess in the casing and which has a screw-threaded connection with said valve stem, said bushing having non-rotative interlocking connections by means of endwise projecting lugs at one of its ends with a part which is normally stationary with respect to the casing and an annular detachable part engaging the casing and bearing on one end of the bushing to hold same in place in said recess. This valve has a permanent hollow cap centrally apertured for the passage of the valve stem there through to retain the plug and does not employ a snap ring for retaining the plug nor does it use an external tool for operating the valve.
The Albert J. Weatherhead Jr. patent disclosed an angle valve with a permanent stem machined with a plug seat and threaded to screw in and out through a female threaded bushing through a permanent and integral cap bored to allow passage of the stem.
Removal of the stem and plug is prevented not by a snap ring but by part of the valve itself and does not require an external and added tool to open and close the valve and therefore in not the type of valve for which the "Retaining Snap Ring Adapter" is designed.